New applications and uses for microelectromechanical systems (MEMS) are continuously being developed. Many microelectromechanical systems typically include one or more microactuated devices that are machined into silicon wafers or other substrates in part using many of the batch fabrication techniques developed for fabricating electronic devices. Microactuated devices typically include movable members or components that either are driven by an electrical stimulus to perform mechanical tasks or are sensory elements that generate an input to an electronic system in response to a physical stimulus or condition. In addition, by virtue of the commonality of many manufacturing processes, control and other support electronics may also be fabricated onto the same substrates as the microactuated devices, thereby providing single chip solutions for many microelectromechanical applications.
For example, one general application of microelectromechanical systems is that of fluid delivery or regulation systems, e.g., in biomedical or biological applications such as portable or implantable drug delivery systems, biochemical analysis applications such as chip immuno sensors and portable gas chromatographs, air flow control applications such heating, ventilation and air conditioning systems, robotics applications such as effectors for microrobotic manipulators, food and pharmaceutical applications such as mass flow controllers, and micro fuel injectors and valving systems, among others.
A micropump, for example, is a microelectromechanical device suitable for use in the delivery of fluid between two ports. Similarly, a microvalve is a microelectromechanical device suitable for use in selectively permitting or blocking passage of a fluid through a port. Bidirectional peristaltic micropumps have also been developed which couple a pump actuator with two peristaltic microvalves. By controlling the exciting sequence of the two valves and the pump actuator, a pumping operation in either direction between two ports may be achieved.
Another general application of microelectromechanical systems is in sensors such as differential or absolute fluid or gas pressure sensors, accelerometers, and the like. In such applications, a microelectromechanical device may include a sensory member coupled to electronic processing components that sense movement of the sensory member.
However, it has been found that many conventional micropumps and microvalves require high drive voltages to attain adequate fluid delivery rates for many applications. For example, micropumps and microvalves have been developed that rely on electrostatic motive forces and require drive voltages of several hundred volts. If used in conjunction with conventional signal control or other processing electronics (whether or not on the same substrate), often a separate power supply or voltage regulator is required to drive such microelectromechanical devices, since most electronic processing devices operate in the range of 1-5 volts. Moreover, in many biomedical or biological applications a serious safety concern is raised with respect to such devices by virtue of the potential for electrical breakdown at high voltages. Furthermore, it has also been found that many microelectromechanical sensors provide low output levels that require delicate and highly complex electronics to adequately sense and process the sensory output of a sensory member.
Electromagnetic force has been used in other microelectromechanical systems such as micromotors and the like. In addition, it has been proposed to use electromagnetic force as a motive force in micropumps and microvalves. The proposed designs rely on an external electromagnetic coil wrapped around a fluid delivery tube in which has been mounted a soft metal diaphragm. Electromagnetic force is applied around the perimeter of the diaphragm by the external coil. However, the designs, and particularly the external coils utilized therein, are not well suited for batch processing, and thus are poorly adapted for mass production. Moreover, the designs are rather bulky in practice and are difficult to incorporate into integrated systems, thereby likely requiring additional support circuitry that further increases the overall size, cost and complexity of such systems.